Learning serial port communication under the Linux operating system

### I. What is Serial Communication?

Serial communication refers to the serial transmission of data between a computer host and peripherals, as well as between host systems. When using serial communication, each character sent and received is actually transmitted one bit at a time, with each bit being either 1 or 0.

### II. Classification of Serial Communication

Serial communication can be divided into two categories: synchronous communication and asynchronous communication. Synchronous communication sends and receives data according to software-identified synchronization characters, while asynchronous communication is a type of communication method that uses character re-synchronization technology.

#### 2.1 Synchronous Communication

Synchronous communication is a continuous serial data transmission method where only one frame of information is transmitted during a single communication session. The information frame here differs from the character frame in asynchronous communication and usually contains several data characters. For example, as shown in the figure: